Có thể có các tripeptit

        +) Gly – Ala –Phe

    H₂ N-CH₂-CO-NH-CH(CH₃ )-CO-NH-CH(CH₂-C₆ H₅ )-COOH

        +) Gly – Phe – Ala

    H₂ N-CH₂-CO-NH-CH(CH₂-C₆ H₅ )-CO-NH-CH(CH₃)-COOH

        +) Ala – Gly – Phe

    H₂ N-CH(CH₃ )-CO-NH-CH₂-CO-NH-CH(CH₂-C₆ H₅ )-COOH

        +) Ala – Phe – Gly

    H₂ N-CH(CH₃ )-CO-NH-CH₂ (CH₂-C₆ H₅)-CO-NH-CH₂-COOH

        +) Phe – Gly –Ala

    H₂ N-CH(CH₂-C₆ H₅ )-CO-NH-CH₂-CO-NH-CH₂ (CH₃)-COOH

        +) Phe – Ala – Gly

    H₂ N-CH(CH₂-C₆ H₅ )-CO-NH-CH(CH₃)-CO-NH-CH₂-COOH